Anthropogenic sustained increase in near bottom suspended particulate matter concentration of the deep marginal sea

Anthropocene sediment flux from land to sea has quadrupled from 1950 to 2010, mainly due to mineral extraction. The distribution of suspended particulate matter (SPM) in the deep sea influences the marine environment, sedimentation processes, and material cycling. Using long-term survey data and published findings, we observed an upward trend in near-bottom SPM across three representative marginal seas by profile data from the same month or season with time spans ranging from 3 to 10 years. In the South China Sea, four stations indicate a consistent increasing trend in near-bottom SPM, with an average increase of more than twofold, although the rate of increase varied across different regions and depths. Similarly, profiles from the Gulf of Mexico and the Mediterranean Sea also demonstrated an upward trend in near-bottom SPM. These three marginal seas are known hotspots for bottom trawling, with frequent engineering activities and mining. Human activities, especially bottom trawling, are identified as the primary drivers behind the ongoing increase in near-bottom turbidity in these marginal seas. As human activities continue to escalate, it is anticipated that near-bottom SPM in these marginal seas may rise in the future. • The upward trend in near-bottom SPM was observed by profile data from same month or season with time spans ranging from 3 to 10 years. • The rate of increase varied across different regions and depth, with an average increase of more than onefold in near-bottom SPM. • Human activities, especially bottom trawling, are identified as the primary drivers behind the ongoing increase in near-bottom turbidity in these marginal seas.